An active matrix liquid crystal display panel typically includes an active matrix substrate, a counter substrate disposed facing the active matrix substrate, and a liquid crystal layer provided between the two substrates. The active matrix substrate includes a switching element, e.g. a thin film transistor (TFT), for each pixel. A display region of the liquid crystal display panel is defined by a plurality of pixels in the active matrix substrate. Drive circuits and the like are mounted or formed monolithically in a non-display region (also called a “frame region”) in the periphery of the display region.
Liquid crystal display panels employing transverse electrical field modes, liquid crystal display panels employing Vertical Alignment (VA) modes, and the like, for example, are widely used as active matrix liquid crystal display panels having wide viewing angle characteristics.
In-Plane Switching (IPS) mode liquid crystal display panels and Fringe Field Switching (FFS) mode liquid crystal display panels are examples of transverse electrical field mode liquid crystal display panels. In a transverse electrical field mode liquid crystal display panel, an electrical field is produced in the liquid crystal layer in a direction parallel to the substrate surfaces by applying voltages to pixel electrodes and common electrodes (also called “counter electrodes”) formed on the active matrix substrate. In a VA mode liquid crystal display panel, which is a vertical electrical field mode liquid crystal display panel, an electrical field is produced in the liquid crystal layer in a direction perpendicular to the substrate surfaces (a vertical direction) by applying a voltage to pixel electrodes and counter electrodes disposed facing each other with the liquid crystal layer located therebetween. Examples of VA mode liquid crystal display panels include Multidomain Vertical Alignment (MVA) mode liquid crystal display panels, where a plurality of domains in which the liquid crystal molecules are aligned in different directions are formed in a single pixel, and Continuous Pinwheel Alignment (CPA) mode liquid crystal display panels, where the directions in which the liquid crystal molecules are aligned are varied continuously central to a rivet or the like formed on an electrode in a central part of the pixel.
Generally, the thickness of the liquid crystal layer of a liquid crystal display panel (also called the “cell gap”) is defined by spacers disposed between the active matrix substrate and the counter substrate. In addition to being disposed within the display region, the spacers are sometimes disposed in the non-display region as well. There are also situations where spacers (granular spacers) are mixed into a sealing material for laminating the active matrix substrate to the counter substrate.
As the resolutions of liquid crystal display panels increase, methods in which photolithography processes are used to form spacers in predetermined locations are being widely employed. Spacers formed in this manner will be called photo spacers (sometimes abbreviated as “PS”).
Although usually formed on the counter substrate (a color filter substrate), photo spacers are sometimes provided on the active matrix substrate.
The liquid crystal display panel illustrated in FIG. 40 of PTL 1 is a FFS mode liquid crystal display panel, and a photo spacer is disposed corresponding to each pixel. Each photo spacer is formed on the active matrix substrate while overlapping with a gate bus line when viewed from a direction perpendicular to the substrate surface. Forming each photo spacer in the same location relative to the corresponding pixel makes it easier to ensure that the photo spacers have a constant height. This is because an active matrix substrate has, for example, TFTs, gate bus lines, source bus lines, and the like on the surface of a glass substrate, and thus the surface is not necessarily flat; furthermore, the intensity distribution of light used in the exposure step for forming the photo spacers is not uniform. According to PTL 1, the photo spacers are formed using a synthetic resin film that levels the surface of the active matrix substrate prior to the common electrodes being formed. In the liquid crystal display panel illustrated in FIG. 40 of PTL 1, the photo spacers are disposed in a flat region above the gate bus lines.